a) Field of the Invention
The invention is directed to a vacuum control valve. More specifically, the invention is directed to a vacuum control valve with a controllable opening cross-section, comprising a valve chamber with a valve opening and a closing body, wherein an operating device for the closing body is provided which comprises a valve rod to which the closing body is affixed and a drive device, and the opening cross-section of the valve is controllable by changing the position of the closing body by means of the operating device.
b) Description of Related Art
Vacuum valves in the shape of a corner valve whose valve chamber has connection flanges arranged at an angle to each other are known. To close the valve, a valve gate arranged on a valve rod is placed against a valve seat in the valve chamber. The valve rod leaves the valve chamber via a feedthrough situated opposite to the valve seat. Such vacuum corner valves are, for example, known from DE 40 23 845 C1 and the U.S. Pat. No. 3,108,780.
Construction of such corner valves as control valves is furthermore known. For controlling the conductance of the valve, the closing body realized as a valve disk is lifted away from the valve seat in a controlled manner, but this only permits a very rough control of the opening cross-section. For a better control of small conductances, providing an opening in the valve disk which in the closed state of the valve is closed by another, smaller valve disk has already been suggested. Lifting the smaller valve disk away from the opening in the big valve disk can be controlled. To improve control behavior, the smaller valve disk could have a conical portion that protrudes into the opening in the big valve disk. Apart from the relatively complicated construction, such a control valve has the disadvantage that for small conductances, the production tolerances of the smaller valve disk, the sealing washer, and the valve seat of the small valve disk strongly influence control behavior.
A combined quick-acting gate valve and control valve intended in particular for the use in steam turbines is known from DE 30 18 093 A1. The control valve has a valve-closing piston that is arranged in a circular cylindrical area of the valve opening so that it can be moved. This closing piston has a ring-shaped flow-conducting channel with an approximately radial inlet and an approximately axial outlet. If the valve-closing piston only plunges into the cylindrical area of the valve opening to the start of the ring-shaped flow-conducting channel, the entire inlet cross-section of the flow-conducting channel is available. To control the flow of steam, the valve-closing piston is plunged in further so that the inlet of the flow-conducting channel is to a lesser or greater degree. A valve-closing cone is connected to the valve-closing piston. In the completely closed position of the valve, the valve closing cone lies in contact with the cone seat adjacent to the cylindrical portion of the valve opening; by means of this, the steam flow through the valve is completely cut off. This valve is not a vacuum valve and the maximal cross-section of the opening of the valve is determined by the opening cross-section of the flow-conducting channel.
From DE-PS 160 700 a control valve for feeding steam radiators is known which has flow controlling openings in the closing part.
Valves with closing parts whose shape widens into a cone are known in different embodiment forms. An embodiment example of such a valve is, for example, shown in U.S. Pat. No. 4,909,477.
It is an important object of the invention to provide a vacuum control valve that makes precise control of small conductances possible.
It is a further object of the invention to provide a vacuum control valve that has a large control range.
It is a further object of the invention to provide a vacuum control valve that is vacuum-tight in its closed state.
It is a further object of the invention to provide a vacuum control valve that is of a simple construction and that can be produced in a simple and cost-effective manner because of its insensitivity to production tolerances.
A vacuum control valve according to the invention comprises:
a valve chamber with a valve opening which has a portion with a cylindrical inside wall on which an elastic sealing washer is provided;
a closing body which comprises a cylindrical portion with a first end and a second end adjoined by a portion of the closing body that widens into a cone, wherein at least one groove is present in the cylindrical portion of the closing body which extends to the first end of the cylindrical portion and which either widens along its extent to the first end, or deepens, or widens as well as deepens;
an operating device for the closing body which comprises a valve rod to which the closing body is attached and a drive device, wherein the closing body can be moved by means of the operating device, from a completely open position of the valve where the closing body has been pulled out of the elastic sealing washer, through a control range where the sealing washer encloses the cylindrical portion of the closing body, to a completely closed position where the portion of the closing body that widens into a cone is pressed against the sealing washer.
In an advantageous embodiment form of the invention, a portion of the closing body that narrows conically to form an insertion chamfer for the protection of the sealing washer adjoins the first end of the cylindrical portion.
Furthermore, in a preferred embodiment form of the invention, the groove has a starting point that lies at a distance from the second end of the cylindrical portion.
Further advantages and details of the invention are subsequently to be explained using the embodiment example shown in the drawings from which further objects of the invention also emerge.